In computer technology, a wavetable is a table of stored sound waves that are digitized samples of actual recorded sound. A wavetable is stored in read-only memory (ROM) on a sound card chip but it can also be supplemented with software. Originally, computer sounds (digital versions of analog waveforms) were generated through frequency modulation (FM). Pre-storing sound waveforms in a lookup table improved quality and throughput, but it requires large memory space to store.
Another method for creating instrumental sound is physical sound modeling. Three basic types of models are useful nowadays for musical sound generation: instrument models, spectrum models and abstract models. Instrument models attempt to characterize sound parameters at their mechanical/acoustic source, such as different kinds of timbre of flute, violin, piano, guitar and so on.
To synthesize sounds, we generally want to model an entire timbre family. This can be done by analyzing single tone and note transition performed on the instrument, and building a database that characterizes the whole instrument or any desired timbre family, from which new sounds are synthesize. In the case of the sound processing application, the goal is to manipulate any given sound, that is, not being to restrict to isolated tones and not requiring a previously built database of analyzed data. Thus, the large memory space is not necessarily required.
Another method for creating timbre is to model characteristic of musical instrument in which a reference timbre feeds. Please refer to FIG. 1, which shows a musical instrument with acoustic transducer in the prior art. The musical instrument 16 includes a sound transducer/filter 11, a processor 8, a reference profile memory 7, an adjustable amplifier and a difference former 14. A reference sound is generated directly by a sound generator 10 of a musical instrument 9 or with the use of a loudspeaker 5 by a reference instrument 2, which is made up of a sound generator 3 and a reference sound transducer 4. Then, this reference sound is picked up by a microphone 6. The microphone 6 is connected to a reference memory 7, which makes it possible to store a reference profile 1. The reference memory 7 is connected to a signal processor 8, which supports in particular a statistical evaluation of the sound impression picked up by the microphone 6.
The reference profile 1 can be acquired, for example, by recording a sufficiently long musical performance on a specific reference instrument 2 and by using the signal processor 8 to evaluate it with respect to the characteristic frequency response of the reference instrument 2 or its reference sound transducer 4.
In FIG. 1, the sound generator 10 is connected to a sound transducer 11. The sound transducer 11 generates an acoustic signal, which is sent directly or by the use of a loudspeaker 12 to an environment. The current characteristic profile 13 of the sound transducer 11 is sent to a difference former 14, which evaluates the reference profile 1 as a second input variable. The output signal produced by the difference former 14 is sent under consideration of an amplification 15 to the sound transducer 11 and parameterizes its physical sound. It is thus possible to bring the sound impression of the transducer 11 very close to the sound impression of the reference instrument 2.
Although the characteristic of the reference sound transducer 4 is evaluated, it is also expected that a précised method to estimate frequency response of the entire musical instrument including the filter 11, the amplification 15 and other stage.